The nature of passengers’ injuries from the Russian jet that crashed in Egypt’s Sinai on Saturday may indicate that an explosion took place aboard before the plane hit the ground, an Egyptian doctor who examined the bodies said, Sputnik news agency reported.

Earlier, Russian tabloid LifeNews claimed to have obtained the results of a forensic medical examination that allegedly stated that the passengers “in the tail section of the liner died because of so-called blast injuries.”

According to the broadcaster, they were diagnosed with burns of over 90 percent, with experts noting particles of metal and aircraft covering piercing the bodies of the deceased.

The people in the front part of the plane died from different causes, including blood loss, shock, open head injuries and multiple fractures, it added.

However TASS news agency cited Russian and Egyptian experts as saying that they failed to find any blast-related trauma during their preliminary examination of the bodies of the victims.

“There were no signs of an explosion impact found during the preliminary examination,” the source said.

One of the Egyptian experts also told TASS that “there were no signs of external impact” found on the bodies.

There have been no official announcements made so far on the results of forensic medical examination of the crash victims.

An unnamed US official said on Tuesday that before the Russian passenger airliner crashed in Sinai, an American infrared satellite had detected a heat flash in the same vicinity, indicating that an explosion may have occurred onboard.

“The flash, which was observed by the satellite, that’s a piece of evidence, but against it’s inconclusive. It can also occur if there was a missile attack, a fire onboard or an explosion onboard,” retired flight commander, Sultan Mahmoud Hali, told RT.

Dr. Anil Padhra, a senior lecturer in aviation studies at London’s Kingston University, told RT that examining the passengers’ injuries might not be the most precise way to learn about the reason for the crash.

“It’s too early to say categorically whether or not the plane broke up in the air. It’s difficult to tell what the injuries would have been if there was an explosion onboard. And I think it’s difficult to tell how it would be different to injuries sustained when the bodies impacted the ground,” Padhra said.

The explosion of the engine could have caused the Russian plane crash as it went down right after finishing the climbing stage, when “the engines are under the most stress.”

Dr. Padhra also mentioned another theory, which has been discussed as widely as others, saying that a midair collision could have interrupted the Airbus A321’s flight.

There is a “possibility that the aircraft could have collided with some other object – I’m thinking, in particular, unmanned aerial vehicles or drones may have been operated in that area to gather intelligence by different authorities… We know it was a conflict area. We know that drones can achieve that kind of altitude,” he said.

All 224 people aboard were killed, making it the deadliest civilian aircraft disaster in Russian and Soviet history.

Since the crash on October 31, several possible causes of the Sinai tragedy were discussed by experts.

Islamic State

Islamic State (formerly ISIS/ISIL) attempted to claim responsibility for the incident, saying that it brought the plane down as retaliation for Russian air operation against the terrorists in Syria.

However, many experts rejected the claim, saying that the jihadists only possessed man portable air defense systems with no capability to reach the high-flying Airbus.

Bomb on board

An explosion of a bomb aboard the plane was mentioned as another possible cause of the crash.

US global intelligence company Stratfor said that Egyptian security personnel often take bribes for allowing passengers to avoid checks, with cargo security screenings in the country also not being strict enough.

Mechanical damage

There was also speculation that corrosion of parts of the plane could have caused the crash, backed by claims that the Russian airliner broke up in the air.

However, Egypt’s civil aviation ministry said on Tuesday there are no facts to substantiate assertions that the plane really fell apart in the sky.

The journalist also found out that the Airbus A321 struck its tail on a runaway during an unsuccessful landing in 2001. It was later repaired, but some experts believe the lasting damage could have causing the crash in Egypt.

Russian first class pilot Andrei Litvinov shared his belief with Kommersant newspaper that the Sinai tragedy happened due to "old metal parts, an old aircraft that was already damaged.”

Human error was also mentioned among the early explanations for the incident, but this was quickly rejected.

Ex-flight commander Hali stressed that “it’ll probably not be possible to make any serious comment on the cause of the accident until the black box has been examined.”

“It normally takes four to five weeks to examine the contents of the black boxes because it’s a technical process,” he added.